1. Field of Inventions
The present inventions relate generally to electrophysiology probes such as catheters and surgical probes and, more particularly, to electrodes for use with electrophysiology probes.
2. Description of the Related Art
Catheters, surgical probes and related electrophysiological devices (together referred to herein as xe2x80x9celectrophysiological probesxe2x80x9d or xe2x80x9cprobesxe2x80x9d) are used today in diagnostic and therapeutic medical procedures that require surgical or minimally invasive access to targeted tissue areas within interior regions of the body. The probes include support bodies that typically carry an array of linearly spaced electrodes at the distal end thereof. Probe power control systems that allow physicians to individually control the power applied to the electrodes in such multiple electrode probes are also available. One example of such a system is disclosed in U.S. Pat. No. 5,545,193.
Precise positioning of the electrodes is of paramount importance in all probe-based procedures. However, the need for careful and precise positioning of the electrodes is especially critical during certain procedures concerning the heart. These procedures, called electrophysiological therapy, are becoming more widespread for treating cardiac rhythm disturbances. Cardiac tissue coagulation (sometimes referred to as xe2x80x9cablationxe2x80x9d), where therapeutic lesions are formed in cardiac tissue, is one procedure in which the ability to precisely position the electrodes is especially important. During catheter-based procedures, a physician steers the catheter through a main vein or artery into the region of the heart that is to be treated. In surgical probe-based procedures, the distal portion of the probe is inserted through the patient""s chest and directly into the heart. The physician must then precisely place the linear array of electrodes near the cardiac tissue that is to be coagulated. Fluoroscopic imaging in often used to identify anatomic landmarks within the heart and to position the electrodes relative to the targeted tissue region. Once the electrodes are properly positioned, the physician directs energy from the electrodes to the tissue to form a lesion.
Rigid ring-shaped electrodes were originally used in electrophysiological probes. In recent years, coil electrodes have been introduced in order to increase the flexibility of the distal portion of the probes, thereby enabling the physician to more precisely control the position and shape of the distal portion of the probe and to achieve superior tissue contact. The metals used to manufacture conventional coil electrodes have been heretofore selected according to certain mechanical properties, the primarily property being resiliency. A relatively high level of resiliency is required during the various manufacturing processes, such as coil winding and the mounting of coils onto a probe, because relatively resilient material returns to its original shape after being manipulated during manufacturing, as compared to softer, less resilient materials such as platinum or gold which can be permanently deformed during manufacturing. Relatively resilient materials are also more durable than softer, less resilient materials. Another desirable mechanical property is stiffness. Accordingly, coil electrodes have been formed from relatively resilient and stiff materials and, more specifically, from stainless steel.
The radiopacity of stainless steel is, however, relatively low. Thus, while otherwise superior to coil electrodes formed from less resilient materials such as platinum or gold, stainless steel coil electrodes are difficult to visualize using fluoroscopic imaging techniques. The low visibility of conventional stainless steel coil electrodes makes it difficult to properly position the distal portion of the probe. It is also difficult to differentiate between individual coil electrodes which, in turn, makes individual control of the electrodes difficult even when the distal portion of the probe is properly positioned. The difficulties associated with electrode differentiation are further compounded when the probe includes a relatively large number of electrodes.
One proposed solution to this problem has been to include radiopaque markers on probes in addition to the electrodes. The inventors herein have determined that this proposed solution is less than optimal because the electrodes must be closely spaced in order to insure reliable creation of contiguous lesions between adjacent electrodes. The close spacing precludes the placement of radiopaque markers between the electrodes.
The inventors herein have determined that a need exists for an electrophysiology probe having coil electrodes that are both resilient and radiopaque. Accordingly, one object of the present invention is to provide an electrophysiology probe having one or more coil electrodes that have relatively high levels of resiliency and radiopacity. Another object of the present invention is to provide an electrophysiological probe having an electrode arrangement that facilitates electrode identification.
In order to accomplish some of these and other objectives, a coil electrode for use in an electrophysiology probe in accordance with a present invention is formed from a first material having a relatively high radiopacity and a second material having a relatively high resiliency. In one embodiment, the electrode includes a stainless steel cladding over a relatively soft 90/10 platinum/iridium core. The stainless steel cladding provides the necessary levels of durability and resiliency for coil winding and assembly, while the platinum/iridium core provides the necessary level of radiopacity.
In order to accomplish some of these and other objectives, an electrophysiological probe in accordance with a preferred embodiment of a present invention includes a support structure, at least one first electrode defining a first radiopacity supported on the support structure and at least one second electrode defining a second radiopacity supported on the support structure, the second radiopacity being greater than the first radiopacity. In one embodiment, the probe includes a plurality of first and second electrodes arranged in a predetermined pattern. When viewed under a fluoroscope, the pattern of objects having relatively high and low radiopacities allows the physician to distinguish between individual electrodes.